Process for the production of color photographic images by the silver-dye-bleach process



United States Patent 3,527,603 PROCESS FOR THE PRODUCTION OF COLORPHOTOGRAPHIC IMAGES BY THE SILVER- DYE-BLEACH PROCESS Bernhard Seidel,Cologne-Mulheim, Jakob Kemmer, Co-

logne-Klettenberg, and Erich Bockly and Eberhard Gunther, Leverkusen,Germany, assignors to Agfa- Gevaert Aktiengesellschaft, Leverkusen,Germany, a corporation of Germany No Drawing. Filed Mar. 24, 1967, Ser.No. 625,609 Int. Cl. G03c 7/02, 7/52 US. CI. 96-20 1 Claim ABSTRACT OFTHE DISCLOSURE Sensitivity of silver-dye-bleach layers are increased ifthe bleaching step is carried out with a bleach bath that is flushedwith inert gas like nitrogen, or the layer just before it enters thebleach bath is rinsed in a similarly flushed rinse bath.

. sion is, of course, greatly reduced. Due to the reduction insensitivity azo dyes containing photographic materials for thesilver-dye-bleach process are not only useless for taking photographsbut are generally inferior to photographic copying materials of theconventional composition containing color couplers.

The insuflicient sensitivity constitutes one of the major disadvantagesof this process.

In order to overcome this disadvantage, it has already been proposedthat up to the moment of exposure to light, only colorless precursorswhich subsequently produce azo dyes should be incorporated in thelayers, and after exposure and black-white development, these arereacted with suitable diazonium salts to form the desired image dyeswhich are subsequently bleached.

This process is, however, of no practical significance since there is noknown diazonium salt which will at one and the same time yield suitableyellow, magenta and cyan dyes with three given coupling components.Further more, diazonium salt solutions capable of coupling are toounstable for storage. It is among the objects of the present inventionto modify the silver-dye-bleach process in order to obtain a highersensitivity of the azo-dye containing photographic material.

We now have found that the sensitivity of silver-dyebleach materials canbe increased by flushing the dyebleach bath with an inert gas,preferably nitrogen, during the dye-bleach process or by using a bathsaturated with an inert gas. By using this process improvements in thesensitivity, usually amounting to 0.1 to 0.9 unit log. I -t (where 0.3unit log I -t correspond to an increase in sensitivity of one aperturestop) and considerable improvements in the fogging values, have beenachieved.

In addition, a substantial improvement in the uniformity andreproducibility of processing is achieved. The process according to theinvention may, for example, be performed as follows:

Before processing, the dye-bleach bath is saturated with an inert gas,preferably nitrogen. Alternatively the dyebleach bath is saturated withthe inert gas and a current of inert gas is also maintained duringprocessing. The inert gas may be introduced either in a continuousstream or intermittently. One may also wash or saturate the rinse bathsimmediately before the dye-bleach bath with inert gas in order to removeair from the photographic material to be bleached.

The process according to the invention is thus characterized by the factthat dyebleaching is accomplished in a bath which has been substantiallyor completely freed from dissolved oxygen by being saturated with inertgas. This means that, in practice, there is increased utilization of theimage silver for the dye-bleach process, which results in an increase insensitivity of the color photographic material processed in thedye-bleach process.

It has been found that the use of the inert gas is only effective in thedye-bleach bath and the baths immediately preceding it. Dye-bleachingmay be performed either with a single bath or a sequence of two or morebaths (in cases in which the dye-bleach process is accomplished in twoor more steps). The inert gas treatment completely lacks the aboveeflect when carried out in the black-white developer.

The process according to the invention is thus basically dilferent fromtreating the color developer with nitrogen in color-forming development,where the essential effect of the nitrogen treatment is the mechanicalmotion in the developer caused by the ascending gas bubbles and theprevention of atmospheric oxidation of the developer substance. In thelatter case, the efiect of the inert gas is greatly assisted by reducingagents such as hydroxylamine or alkali metal sulfite added to thecolor-forming developer. Freshly prepared color developers which havethe analytical concentration of developer substance accordingly exerttheir full effect, and the flushing or saturation with inert gas merelyserves to maintain this state as long as possible.

The process according to the invention, on the other hand, provides abath which is distinctly superior to a freshly prepared bath. The efiectof the process according to the invention was all the more unexpectedsince most bleaching baths used in practice, especially those based onthiourea or on quinoline-iodide already contain reducing agents.Moreover, the effect of the process according to the invention cannot beachieved by adding other reducing agents.

The eifect of the saturation with inert gas can be eliminated byflushing with air or oxygen and can be restored by renewal ofintroduction of nitrogen.

The process according to the invention also has the advantage that,owing to the better utilization of dye and silver, it is possible to useimage layers with correspondingly lower silver halide content. Theinventive process in addition makes it possible to work with adye-bleach bath which is not as strongly acid as usual.

Bleaching in the presence of inert gas may also be applied for reducingthe quantity, e.g., of a bleaching catalyst, so that discoloration ofthe layer by the action of the catalyst is avoided.

The process according to the invention is, of course, not limited to thebleaching of a silver image after blackwhite negative development, butcan equally well be applied to the bleaching of positive silver imagessuch as those produced in reverse development or in direct positiveprocesses, e.g., by the bromine ion diffusion process, the silver saltdiffusion process or photosolubilization.

3 EXAMPLE 1 The following layers are applied to a baryted paper support:

1) A silver bromide gelatin emulsion which contains, per kilogram, g. ofa cyan dye of the following formula:

SOaH 503B the preparation of which has been described in GermanAuslegeschrift No. 1,041,355, and mg. of a sensitizer disclosed inGerman Auslegeschrift No. 1,213,240, Example 11. The amount of silver inthe finished layer is about 0.5 g. Ag./m.

(2) Intermediate gelatin layer, if desired with additives for inhibitingdilfusion.

(3) Silver bromide gelatin emulsion layer containing, per kilogram, 5 g.of a magenta dye of the following formula:

one-@sm-rrn on the preparation of which is described in GermanAuslegeschrift No. 1,039,840, and 15 mg. of a sensitizer for the greenregion of the spectrum disclosed in German Auslegeschrift No. 1,213,240,Example 2. The amount of silver applied in the finished layer is 0.5 g.of Ag/m. in the form of silver halide. The dye is rendered fast todiffusion by the addition of 1.5 g. of 4,4'-diphenyl-dibiguanide; (4)Intermediate gelatin layer, thickness 1.0-1.2m (5) Yellow filter layerhaving an optical density of 0.5 at a layer thickness of 1 mm.;

(6) Intermediate gelatin layer, thickness 1.0-1.2/,u (7) A slightly lesssensitive silver bromide gelatin emulsion containing, per kilogram, 8 g.of the yellow dye of the following formula:

described in German Patent No. 935,565, Example 1, which layer has beenrendered fast to diffusion by the addition of 3 g. of4,4-diphenyldibiguanide. The amount of silver in this layer is about0.55 g. of Ag/m. in the form of silver bromide;

(8) Protective gelatin layer, thickness 1.2/,u.

The above multi-layered material is exposed in a conventionalsensitometer behind a grey test wedge and processed as follows:

(6) Rinsing in water for 5 min.

(7) Dye-bleaching for 25 min. in a bath of- Quinoline-SO ml.

Sodium hypophosphite-5 g.

Potassium iodide10 g.

Sulfuric acid conc25 ml. 2,3-dimethylquinoxaline0.1 g. Waterup to 1000ml.

Rinsing in water for 5 min.

Bleach-fixing for 10 min. in a bath of- Anhydrous soda-24 g.

Sodium thiosulfate-l25 g.

Tetrasodium ethylene diamine tetraacetate-26 g. Ferric chloride-15 g.

Anhydrous sodium sulfitel3 g. Waterup to 1000 ml.

The sensitometric tests give the following results:

Uniform fog Cyan 0.34 Magenta 0.2

Yellow 0.22

(a) If a sample of the same material is processed in the same way butwith additional saturation of the dyebleaching bath, by first passing avigorous stream of nitrogen through that bath for 60 minutes before itis used,

the following values are obtained after drying:

Cyan Magenta Yellow Uniform fog 0.25 0. l5 0. 19

(=Difierence from above expcrlment) 0. O9 -0. 05 0. 03 Improvement insensitivity over original sample (log I -t) +0. 25 +0. 35 +0. 54

Cyan Magenta Yellow Uniform fog 0. 15 0. 11 0. 17

(Difference from comparison test) -0. 19 0. 09 0. 06 Sensitivitycompared with original sample (log I -t) +0. 30 +0. 55 +0.60

(0) For comparison, the dye-bleach bath is saturated with oxygen beforethe bleaching process 'but no further gas is introduced during thebleaching process. With this method, only incomplete bleaching isachieved and the following fog values are obtained after drying.

Uniform fog Cyan 1.95 Magenta 1.35

Yellow 0.85

The loss in sensitivity is not compensated by increasing the exposuretime. Thus exposure prolonged by the factor 20 results in the followingvalues- Cyan 1.75 Magenta 1.0 Yellow 0.55

lowing values:

Cyan 0.05 Magenta -0.11 Yellow 0.05

1 Sensitivity compared with original sample (log I -t).

(e) If a bath saturated with air according to d) is subsequently treatedwith nitrogen as indicated under a), the following values are obtainedafter drying of the sample:

Cyan Magenta Yellow Uniform fog 0. 23 0. 14 0. 17

(=Dit1erence from original sample)... -0. 11 0. 06 0. Sensitivitycompared with original sample (log I -t) +0. 25 +0.35 +0. 6

Practically the same values are thus obtained as with saturation of thebath without prior treatment with air. Similar figures are obtained ifthe nitrogen treatment follows a preceding saturation with oxygen.

EXAMPLE 2 A photographic multilayer material is prepared as described inExample 1, except that the amount of silver in the individual layers isonly 65% of the values indicated in Example 1. Such a material isbleached in the course of processing as described in Example 1, to givethe following fog values:

Uniform fog C-yan 0.50 Magenta 0.50 Yellow 0.50

A sample which had been processed under the same conditions but in whichthe dye-bleach bath has been saturated with nitrogen and had nitrogenpassed through it at the rate of 600 ml. of nitrogen per minute duringthe dye-bleach process gave, by contrast, the following values:

Cyan Magenta Yellow Uniform fog 0. 19 0. 19 0.21 (Difference from thecomparison sample without nitrogen) -0. 31 -0. 31 -0. 29 Sensitivitycompared with comparison sample without nitrogen (log I t) +0. 25 +0.10+0.23

Similar results are obtained when instead of the dye bleaching bathsmentioned in Example 1, a bleaching bath containing thiourea is used,e.g., a bath such as described in German Patent No. 1,091,429, Example 5G.

EXAMPLE 3 The following layers are applied to a support of whitepigmented cellulose acetate or a support of polyethylene coated paperwhich has been rendered hydrophilic:

(1) A red sensitized silver halide gelatin emulsion layer whichcontains, per 500 g. of a silver bromide-iodide gelatin emulsion having6 mol percent of silver iodide, 2.7 g. of the following cyan dye:

dissolved in 250 ml. of a 2% gelatin solution to which 2.3 ml. of a 30%formaldehyde solution, 0.4 g. of saponine and as plas'ticizer are alsoadded. The amount of silver in the finished layer is about 0.8 g. Ag/m.in the form of silver halide.

(2) An intermediate layer of 2% gelatin solution.

(3) A layer consisting of 500 ml. of green-sensitive silver bromidegelatin emulsion containing 6 mol percent of silver iodide, to whichemulsion are added 2.8 g. of the magenta dye of the following formula:

IFII:

dissolved in 200 ml. of a 2% gelatin solution and 0.4 g. of saponine,2.3 ml. of a 30% formaldehyde solution and as plasticizer. The amount ofsilver in the finished layer is about 0.75 g. Ag/m. in the form ofsilver halide.

(4) An intermediate layer of a 4% gelatin solution to which are added 8g. of tartrazine per liter.

(5) A layer in which 400 ml. of a 4% gelatin solution containing 0.7 g.of saponine and 4.2 g. of the yellow dye of the following formula:

Cyan Magenta Yellow Uniform fog:

Without N 0. 08 0. l2 0. 17 With N 0.09 0.12 0. 17 Sensitivity increasein the experiment with N flushing (in units log 1-t). +0. 13 +0. 18+0.37

We claim:

1. In the silver-dye-bleach process of producing color photographicimages by the steps of exposing a lightsensitive photographic elementcomprising at least one supported silver halide emulsion layercontaining on a20- dye, developing the exposed layer to form a silverimage therein, and dye-bleaching the azo dye in accordance with thesilver image to form a dye image, the improvement according to which thedye-bleach bath is flushed before or during the dye-bleach process, withnitrogen gas.

References Cited UNITED STATES PATENTS 2,837,988 7/1958 Pavelle -89OTHER REFERENCES Photo Methods for Industry: Gas Burst Agitation,November 1963; pp. 5052 and 54.

Commander F. W. George, M.C., U.S.N.: A Practical System for TelecobaltRadiography, Radiology, The Radiological Society of America, vol. 80,JanuaryJune, 1963, pp. 288-289.

NORMAN G. TORCHIN, Primary Examiner A. T. SURO PICO, Assistant ExaminerUS. Cl. X.R. 96-53

